Electrostatic spray coating systems



Oct. 18, 1966 TILNEY ETAL 3,279,421

ELECTROSTATIC SPRAY COATING SYSTEMS Filed April 1, 1963 4 Sheets-Sheet luuuuununnunnn INVENTORS. RICHARD TIL/VEY, YJOHN Geo/2G5 Cam ew G0FFEY JA5 Lmpus Oct. 18, 1966 R. TILNEY ETAL ELECTROSTATIC SPRAY COATING SYSTEMS4 Sheets-Sheet 5 Filed April 1, 1965 5 S M l Y O Y P I F am 0 WNRS f VMW 7 N 50 I GJ W m y H N F l K H W W w Oct. 18, 1966 R. TlLNEY ETALELECTROSTATIC SPRAY COATING SYSTEMS 4 sheets-sheet 4 Filed April 1, 1965.YIM Z T R mmc v 5 m e e 00 m W United States Patent 3,279,421ELECTROSTATIC SPRAY COATING SYSTEMS Richard Tilney and John GeorgeCampbell, London, and

Geoffrey James Liddle, Christchurch, England, assignors, by mesneassignments, to Ransburg Electro-Coating Crp., Indianapolis, Ind., acorporation of Indiana Filed Apr. 1, 1963, Ser. No. 269,442 Claimspriority, application Great Britain, Apr. 3, 1962, 12,704/ 62 7 Claims.(Cl. 1182) This invention relates to electrostatic spray-coating systemsof the type in which deposition of the spray upon the article beingcoated is promoted by means of a high volt-age electrostatic fieldmaintained between the article and a charging electrode for the spray.The invention is especially, but not exclusively, applicable to anapparatus in which each spray is produced by a rotating, electricallycharged atomizing head of the general type set forth, for example, in U.S. Letters Patent No. 2,893,894 granted on the application of E. M.Ransburg.

In commercial electrostatic spray coating systems, it is common to mountthe articles on a conveyor which moves them past the atomizers toreceive the spray there from. When atomizers of the general typedescribed in the aforesaid Rams-burg patent are employed, it isessential for best results that the distance between each atomizer andthe surface receiving its spray be maintained within apropriate limits.Relatively small articles present no problem in this regard, and thesame is true of some relatively large objects, such as refrigeratorcabinets, which possess a comparatively regular shape. However, when theobjects are both relatively large and irregular in shape, it isfrequently neccesary, in order to maintain appropriate distances betweeneach atomizer and the surface receiving its spray, to move the atomizerstransversely of the article path as the article passes through thecoating zone. Articles of irregular shape frequently present anadditional problem in regard to the aspect of the atomizing headrelative to the spray-receiving surface; for if the plane of the edge ofthe rotating atomizing head departs too far from parallelism with thesurface receiving the spray, undesirable disuniformity may exist in thefinish produced. Automobile bodies are examples of articles presentingproblems of the type noted, and this invention will be described belowas embodied in a system for painting automobile bodies, although it isto be understood that the invention may find use in the coating of otherarticles.

On form of apparatus suitable for use in the painting of automobilebodies comprises a lower pair of atomizing head-s disposed on oppositesides of the conveyor path at an elevation which adapts them forspraying the lower side portions of automobile bodies moving through thecoating zone. These lower heads are mounted, conveniently with theiraxes approximately horizontal and perpendicular to the path of thearticle movement, on trolleys arranged to be moved toward and away fromeach other in order to maintain the atomizers appropriately positionedrelative to the body surface receiving the respective sprays. An upperpair of atomizers, .adapted primarily to spray the upper side portionsand outer top portions of the body, are likewise mounted on trolleyslocated on opposite sides of the body path and movable toward and awayfrom each other to maintain proper distances between the atomizers andthe body portions receiving their spray. For the purpose of coating themiddle portion of the automobile body, it is preferred to employ anatomizer supported from overhead on a recprocator which will operate,like the previously mentioned trolleys, to maintain a proper distancebetwen the atomizer and the body-surface receiving its spray.

Any of the atomizers mentioned may be carried by a swiveled suport whichcan be anuglarly adjusted during a spraying operation to maintain theproper aspect of the atomzer relative to the spary-receiving surface. Ithas been found that in apparatus for coating automobile bodies it willusually be necessary to provide such a swiveled support only for thecentral, or overheadmounted atomizer.

Power operated means of any appropriate type are operatively associatedwith each of the trolleys, 'with the overhead reciprocator, and witheach swiveled support for the purpose of changing the positions of theatomizers as a body passes through the coating zone. These severalpower-operated means are automatically controlled by mechanism operatingin timed relation with movement of the conveyor. Triggering mechanismresponsive to approach of a body to the coating zone automaticallyinitiates operation of the control mechanism which functions, as thebody proceeds through the coating zone, to control the severalpower-operated means in a manner that will maintain each of theatomizers in proper position at all times during the coating operation.

Further featuers of the invention will become apparent from thefollowing more detailed description and from the accompanying drawingsin which:

FIG. 1 is a diagrammatic side elevation of a conveyor line and anassociated set of atomizers;

FIG. 2 is a diagrammatic plan view of the same apparatus;

FIG. 3 is a vertical cross-section transversely of the conveyor showingan automobile body, the atomizer, and the respective supports inelevation;

FIG. 4 is a diagram indicating the functional control arrangement of .asystem suitable for use with the apparatus shown in FIGS. 1-3;

FIG. 5 is a vertical section through a head-driving and head-positioningmechanism especially suited for use in connection with an overheadatomizer; and

FIG. 6 is a side elevation of the mechanism shown in FIG. 5.

In the apparatus shown in FIGS. 1-3, automobile bodies 10 to be paintedare mounted on wheeled carriers 11 moved along tracks 12 by a conveyorchain 13. The conveyor moves in the direction indicated by arrow 14, andeach body is first subjected to the spray from two heads 15, 16 disposedon opposite sides of the conveyor line, and both facing towards thatline. The heads are mounted upon suitable trolleys 17, 18, which run onguide rail structures 20, 21, so as to move to and from the conveyorline along the rail structures. The function of the heads 15 and 16 isprimarily to coat the lower portions of the side surfaces of the carbody and to a lesser extent other surface portions, as will be broughtout hereinafter.

The spray painting station includes also a further pair of heads 26, 27.These heads are mounted in a fashion similar to heads 15, 16 upontrolleys 28, 29 which are likewise given the facility of movementtowards and away from the conveyor line along rails 31, 32. As will beseen from FIGS. 1-3, the heads 26 and 27 are desirably mounted so thatthey can spray the upper portions of the body-sides and the edgeportions of the body-roof.

The middle portion of each body is coated with spray from a head 34supported from overhead by mechanism 35 operable to control the verticalposition of the head. In the particular embodiment illustrated, the head34 is mounted on the mechanism 35 through a swiveling device 36 by whichthe position of the head can be angularly varied, in the directionindicated by arrow 39.

It will be understood that each head will have associated with it ahead-rotating motor, as well as means for feeding paint to the head nearthe center thereof, the

paint so fed being delivered in the form of a film to the edge of thehead by centrifugal force.

The trolleys such as 17 18 and 28, 29 can be reciprocated to and fromthe conveyor line by any suitable means, but a simple and effectivemethod of achieving this is shown in FIGURE 3. In this arrangement areversi-ble electric motor 41 drives a pinion 42, engaged at oppositepoints by two racks 43, 44, attached to the ends of a drive cable 45.The cable 45 passes round a series of guide pulleys 46, so as to provide.two spans of cable extending across the line of the conveyor, and thetrolleys, such as 17 and 18, are attached to the spans at oppositelymoving points.

It is arranged that the paint spraying means is operated by the arrivalof a body to be painted, and for this purpose there is provided atriggering device comprising a light source 47 and a photo-electric cellor other detecting device 48. These two parts are so disposed that thelight falling upon the cell is interrupted when a body arrives, and thisis used to initiate the operation. If desired, the system can bearranged to paint automatically different shapes of body. One way ofaccomplishing that result is through the use of one or more additionaltriggering devices each including a light source and photoelectric cell,one such additional device being indicated at 50, 51. The disposition ofthe several triggering devices is such that bodies of difierent shapeswill interrupt difierent sets of light beams; and, through anappropriate discriminating apparatus, the particular set of light beamsinterrupted will condition the control mechanism to perform thehead-positioning and spray-timing.

operations. If, as will frequently be the case, the differences betweentwo body shapes includes a difference in over-all length it will besufiicient to provide two triggering devices so spaced along theconveyor line that the longer body will simultaneously interrupt bothlight beams while the shorter body will interrupt the beams one at atime.

The general functional arrangement of means for automaticallycontrolling an apparatus such as that shown in FIGURES l-3 is indicatedin FIGURE 4. Conveniently, the automatic control means comprises one ormore drum cams each actuating a series of switches through whichoperation of the several head-positioning mechanisms, as well asinitiation and termination of each spraying operation, are controlled.Each cam is driven at a speed coordinated with that of the conveyor 13and is so arranged that its rotation, when once initiated, will continuefor one full revolution to carry the cam from, and return it to, a homeposition. The number of cams employed will vary, depending upon thenumber of different body shapes .the system will be called on to coatand upon whether or not the cycle of operations necessary to coat onebody will be completed before initiation of the cycle involved incoating the next body. In general, one cam or set of two cams will beprovided for each body-shape to be coated, and whether there are twocams or only one for each body-shape will depend upon whether one cycleof operation is initiated before the preceding cycle ends or whetherthere is a time interval between successive cycles.

In the case of the apparatus shown in FIG. 4, it is contemplated thatthere will be an overlapping (in time) of successive cycles and that theapparatus will be called upon to paint bodies of two different shapes.Accordingly, there is provided one set of two earns 55 and 56 for onebody shape and a second set, 55a and 56a, for the other body-shape.Which set of cams 55-56 or 55a- 56a, will operate to control the cycleof operation initiated by approach of a body to the coating zone will bedetermined by a discriminator 57 responsive to signals from the severalcells 48 and 51.

As previously mentioned, each of the heads has associated with it amotor for rotating it. Two of such head-rotating motors are indicated at60, 61 in FIG. 4.

Ordinarily, the rotation of the heads will not be interrupted duringoperation of the complete coating apparatus, and the same is true of thesupply of high voltage to the heads. Accordingly, FIG. 4 shows amanually operated device 62 which controls operation of all thehead-rotating motors and also activation of a high-voltage source 63from which high voltage is applied to the heads over a conductor 64.Preferably the high voltage circuit includes or has associated with it aspark guard 65 which may be of a type commonly used in electrostaticspray-painting systems to deactivate the highvoltage source or otherwiseinterrupt the supply of high voltage to an electrode when any groundedobject approaches the electrode and thereby creates danger of adisruptive dischar e.

Paint is supplied to the atomizing heads from a paintsupply line 67through conduits 68 containing valves 69 which are selectivelycontrolled by the control cams. If desired, the apparatus may be adaptedfor the application of paints of different colors by providing aplurality of paint lines 67 and a set of valves 69 for each paint line.If that is done, it is desirable to include in the apparatus means forflushing the atomizing heads and the conduits leading to them with anappropriate solvent before paint of the new color is supplied. Means ofthis type are known, one such being shown in the copending applicationof James W. Juvinall, Ser. No. 775,316, filed November 20, 1958, nowabandoned.

In addition to controlling operation of the paint-supply valves 69, thecontrol cams also control the mechanisms by which the positions of theatomizing heads are changed as each spraying cycle passes. Each of suchhead-positioning mechanisms includes a reversible motor, two of whichare shown in FIG. 4 at 71 and 72. When it is desired to control not onlythe direction of rotation, but also the speed of operation, of the motorembodied in a head-positioning mechanism, it is convenient to use areversible motor of the hydraulic type. The motor 72 in FIG. 4 is ofthat type. As shown, it is arranged in a hydraulic circuit 73, whichincludes a flow-control valve 74, across the outlet ports of a reversingvalve 75 supplied with fluid under pressure from a pump 76. The controlcams control both the flow-control valve 74 and the reversing valve 75,and the latter is of the known type which can be selectively positionedto cause flow in either direction in the circuit 73 or to interrupt flowin that circuit.

While specific forms of head-positioning mechanisms are described below,this invention, in its broader aspects, is not concerned with details ofsuch mechanisms or with the precise form of other devices controlled bythe control cams. As previously mentioned, the lateral positions of thetrolleys 17, 18, 28 and 29 relative to the conveyor line can becontrolled by reversible electric motors, such as indicated at 41 inFIG. 3. The mechanism 35, which controls the height of the overheadatomizer 34, is conveniently a hydraulic motor of the cylinder andpiston type, and may have an associated speed control like that providedfor the motor 72 of FIG. 4. Valves, such as the valves 69 and 75 of FIG.4, can be controlled by solenoids activated and deactivated by thecontrol cams. A valve, like the flow-control valve 74 of FIG. 4, whichmay have more than three positions, can be operated by an appropriateform of servo mechanism controlled by the control cams.

The apparatus as so far described is conditioned for operation byoperating the manual control 62 to initiate rotation of all theatomizing heads and to activate the high voltage source 63. The conveyor13 is then started to move the bodies 10 successively through thecoating zone. The bodies are grounded through the carriers 11 and tracks12 and hence will attract the charged paint particles discharged fromthe atomizing heads as those heads are successively supplied with paintby operation of the valves 69.

Until the first body reaches the coating zone, the

several atomizing heads will normally be in the positions desired forthem when spraying is to start, such positions being determined by thecontrol cams, all of which will be in their home positions. For mostbodies this means that the heads 15 and 16 will be at their innermostlimits of movement, usually in the path of an approaching body, and thatthe head 34 will be at the lower limit of its movement and also in thepath of an approaching body. The head 34 will be swiveled to an inclinedposition adapted to cause discharge of its spray toward the lowerportion of the front end of the approaching body. Vertically the heads15, 16 and 34 will be so disposed that their sprays will reach thelowermost point of the front end of the approaching body, and the twoheads 15 and 16 will be so positioned laterally of the conveyor that themargins of their deposited sprays will overlap the margin of the spraydeposited from the head 34. In the particular apparatus illustrated,which has been used inthe coating of the bodies for small automobiles,the bells 15 and 16 can be so positioned vertically that their sprayswill both reach the lowermost points at the front and rear ends of thebody and also the side portions of upwardly presented surfaces, such asthe tops of the fenders, the trunk, and the hood, if the hood is inplace. Accordingly, it is unnecessary to provide any mechanisms foradjusting the heads 15 and 16 vertically on the trolleys; but suchmechanisms could be provided if necessary.

As a body approaches the coating zone, one or more of the triggeringdevices will be actuated and will operate, through the discriminator 57,to initiate rotation of one of the control cams. Hereafter it will beassumed that the cam so thrown into rotation is the cam 55. As that camrotates, it will cause operation of valves 69 (FIG. 4) to initiatespraying from the heads at the proper times. After spraying from theheads 15 and 16 has started, the cam 55 will cause the trolleys 17 and18 to move gradually outward to positions in which the heads 15 and 16will clear the approaching body and thereafter to maintain anappropriate distance between each of those heads and the sides of thebody passing it. As the body moves beyond the heads 15 and 16, thecarriages 17 and 18, will be moved inwardly to cause the sprays from theheads 15 and 16 to coat rear end surfaces of the body. As the bodypasses through the coating zone, the head 34 will be moved vertically tomaintain the appropriate distance between it and the body surfacereceiving its spray. Additionally, the head 34 will swivel as necessaryto maintain it as nearly as possible in proper aspect relative to thespray-receiving surfaces. In its final position, approximating thatshown in FIG. 1, the head 34 will be positioned to discharge its spraytoward the extreme rear of the body where the spray it deposits willoverlap that from the heads 15 and 16.

The heads 26 and 27, and the supply of paint thereto, will be controledby the cam 55 in a manner generally similar to that followed in respectto the heads 15, 16 and 34. As shown, the only positonal adjustmentprovided for the heads 26 and 27 is that afforded by in and out.

movement of the trolleys 31 and 32, but if desired those heads could beprovided with positioning mechanisms which function under control of thecontrol cams to vary the elevation of the heads as a body passes throughthe coating zone. Any of the heads 15, 16, 26, and 27 can if desired beprovided with svvivelling supports operable under control of the controlcams to vary the aspect to the head relative to the spray-receivingsurface.

Reference has been made above to the possibility of providing for anyhead-positioning mechanism a variable speed control such as thatprovided for the motor 72 in FIG. 4. In the case of heads whose changeof position can be effected at rates that do not vary too widely asufficiently close approximation to the optimum rate of position-changecan be obtained with constant-speed head-positioning motors byappropriate regulation of the frequency and duration of the intervalsduring which the head is moved. Variable speed control is indicated,however, in the case of swivelling of the head 34; for, while theswivelling of that head may proceed at a relatively low rate as itsspray follows the contours of hood and trunk, a relatively rapidswivelling movement of the head is desirable when the head is in theangle between the hood and the front corner posts of the body or theangle between the rear corner posts of the body and the trunk.Relatively rapid swivelling movement of the head 34 may also benecessary to reverse its position after it has completed the spraypingof one body and before it begins spraying the next. In the particularapparatus illustrated in FIGS. 13, it has not been found necessary ordesirable to provide variable speed control except in the case of themechanism which swivels the head 34.

The positioning of the various a'tomizing heads relative to each otheralong the conveyor line may vary c0nsiderab-ly; but it is desirable thatheads which deposit spray in overlapping patterns should not be spacedso far apart along the conveyor line that the paint deposited by onehead will have dried unduly before the overlapping spray is deposited.The relative spacing of the various heads along the conveyor line willaffect the possibility of beginning the coating of one body before thecoating of the preceding body is completed. For example, if the sprayingfrom all heads is terminated approximately simultaneously, it will beimpossible for the spraying of one body to start before that of theother body is completed; but if those heads which are initially thowninto operation at the institution of a spraying cycle complete theirfunction of coating one body while other heads are still spraying thatsame body, a second cycle may be instituted before the first iscompleted. In the assumed case, where the spraying of the one body isbeing carried out under control of the cam 55, as a second body of thesame shape approaches the coating zone and actuates the triggeringdevice, the cam 56 will be thrown into rotation and will control thecoating of the second body, the cam 55 continuing to rotate until thecoating of the first body is completed and the cam reaches its homeposition ready for operation to control coating of a third body.

The problem of designing mechanisms suitable for rotating the atomizingheads, and also for changing their angular disposition, is one which issusceptible of a variety of solutions but FIGS. 5 and 6 show a form ofdevice which is especially suitable for use with the overhead supportedhead 34. That device comprises a housing 82, which is intended to bemounted upon the moving part of the head-positioning mechanism 35.Mounted within the housing 82 are two drive motors 83 and 84, of whichthe former is reversible and used to cause angular movement of theatomizing head 34, whilst motor 84 is used for rotating the head aboutits axis. Depending from the lower side of housing 82 are two flanged,hollow brackets 85 and 86 of highly insulating material, the lower endsof which are respectively received in and secured to two similarconnectors, 87, 88. A horizontal support sleeve 90 has its endsrotatably received in the connectors 87 and 88, desirably through rollerbearings 91, 92. A hollow head-drive shaft 93 is mounted transversely insleeve 90' by means of bearings 95, 96 and between these bearings thesleeve carries a bevel drive gear 97. A drive shaft 100 mounted in theconnector 88, by means of bearings 101, 102, carries at its inner end afurther bevel gear which meshes with the bevel gear 97. At its outer endthe shaft 100 carries another bevel gear 104, in turn meshing with abevel gear 105' on the end of a vertical shaft 106, which extendsupwardly through the connector 88 and bracket 86 to be driven from motor84 through a resilient coupling means 107. By this means, the drivemotor 84 will drive shaft 106, and through gears 105, 104 the shaft 100.In turn shaft 100 drives the head drive shaft 93 through gears 105 and97. In use, a paint supply tube can be located down the center of thedrive shaft 93, to supply paint to the bell 34, which will be secured tothe lower end of such shaft.

To adjust the angular positon of sleeve 90, motor 83 is coupled througha belt drive 110 to a speed reduction gear box 111. The output shaft 112of the gear box is connected through a flexible coupling 113, to a shaft114, carrying at its lower end within the connector 87 a bevel gear 115,meshing with a similar gear 116 on a transverse shaft 117. Shaft 117 iscarried at its outer end in a bearing 118 in the connector 87, but itsinner end is fast to the sleeve 90. In this way, when the motor 83drives, it will rotate shaft 114, and thus shaft 117, causing angularmove-ment, about a horizontal axis, of the sleeve W and the atomizinghead supported therefrom on the end of shaft 93. The speed reductiongear 111 carries a cam 120, which operates limit switches 121, 122 inorder to protect the apparatus against excessive movement of theconnecting sleeve 96.

The insulating brackets 85 and 86 electrically isolate the sleeve 90 andthe parts, including the head, it carries from the housing 82 and thesupport therefor, thus making it possible to maintain high voltage onthe head. It will be understood that all heads and head-mountings willbe supported through insulating material for the same purpose.

The apparatus described can be set up to give a very high quality anduniform finish on an article such as a car body, eliminating or reducingto a minimum the necessity for hand touch-up. The facility of moving theheads to and from the surface of the body being coated enables theappropriate quantity of paint to be uniformly deposited upon the bodyfrom spray heads which do not approach so closely to the surface beingcoated as to create danger of a disruptive discharge from any head, norrecede too far from the body, which might produce a deleterious eifecton the finish, due to an excessive loss of solvent from the paint spray,thus causing the deposit of dry paint upon the surface being coated,with consequent loss of finish quality. Further, the change of attitudeof a spray atomizing head with respect to the surface being coated alsomay have an important effect upon the quality of the finish. As will beobvious, the attitude of the head can be such that spray particlesleaving one segment of the head-edge may travel farther and become drierbefore being deposited than particles leaving another segment of thehead-edge. If the farthertravelling particles become dry enough and arethe last particles deposited on any given area they will not blend withthe previously deposited paint, and a deterioration in quality of finishwill result. It is therefore desirable to control the attitude of thehead in such a way that spray particles travelling far enough to becomeunduly dry before being deposited will be the first to reach any pointon the surface, so that the later-deposited, wetter particles willproduce blending and a smooth finish. To minimize the likelihood thatthe particles last deposited will be unduly dry it is desirable that,when possible, the head be maintained at all times in an attitude suchthat the distance between the plane of the head-edge and any passingpoint on the body surface will be greater when that point first receivespaint than it is when that point last receives paint.

It has been mentioned above that it is desirable that the heads inoperation should not approach too closely to the grounded surface uponwhich paint is being deposited, for the reason that it may then occurthat the potential gradient across the gap between the two parts will besuch as to give rise to a disruptive discharge. This will not occurnormally once the apparatus has been set up, and protection againstdisruptive discharge will be afforded by the spark guard circuit.However, if a fault should develop in the apparatus damage might becaused by the body being painted, or some part of the conveyor system,colliding with one or the other of the heads or their positioning means.The spark guard 65 can in these circumstances be arranged to giveprotection against any such collision. If the spark guard responds tothe proximity of the car body, it can be arranged that the spark guard,acting through the control drums, will cause the withdrawal of one ormore of the atomizing heads from the path of the approaching bodyportion. In one practical form of the invention, it has been foundadvantageous to arrange that the spark guard causes an initialwithdrawal of the heads in this way; should the spark guard continue torespond, indicating that the Withdrawal is insufiicient, a second stageof withdrawal can take place. If again the spark guard continues torespond, then the apparatus can be shut down, so that the faultycondition can be investigated and remedied. In general, with a highlymechanized sytsem such as is normally adopted for car assembly, it isvery undesirable that a conveyor should be stopped, and the systemdescribed is a compromise which reduces the likelihood of conveyorstoppage.

We claim:

1. Electrostatic spray-coating apparatus, comprising a conveyor forconveying through a coating zone a succession of articles to be coated,a plurality of atomizing devices for spraying liquid coating material onto each article as it passes through the coating zone, means including ahigh-voltage source for creating an electrical charge differentialbetween the spray particles and an article in the coating zone, at leastone of said atomizing devices being mounted on a swivelled support theaxis of which is transverse to the direction in. which spray isprojected from such atomizing device and also transverse to theconveyor, whereby the atomizing device can be directed alternativelytoward either an approaching article or a receding article,power-operated means for swivelling said support, and automatic controlmeans operating in timed relation to the conveyor for controlling saidpower-operated means and the supply of coating material to eachatomizing device.

2. Electrostatic coating apparatus as set forth in claim 1 with theaddition of a carrier arranged for movement transversely to the path ofarticle movement under control of said automatic means, said swiveiledsupport being mounted on said carrier.

3. Electrostatic coating apparatus according to claim 1 characterized inthat each of said atomizing devices comprises a rotating atomizing headelectrically connected to said high-voltage source and from theperiphery of which atomization of the coating material takes place, saidpower-operated means being controlled to maintain said atomizing head insuch an attitude that the plane of its periphery will be approximatelyparallel to the article surface opposite the head.

4. Electrostatic coating apparatus according to claim 1 with theaddition of means controlled by said automatic means for regulating theoperational speed of said poweroperated means.

5. Electrostatic spray-coating apparatus, comprising a conveyor forconveying through a coating zone a succession of articles to be coated,a plurality of atomizing devices for spraying liquid coating material onto each article as it passes through the coating zone, means including ahigh-voltage source for creating an electrical charge differentialbetween the spray particles and an article in the coating zone, at leastone of said atomizing devices being mounted on a carrier arranged formovement transversely of the path of article movement, poweroperatedmeans for cyclically moving said carrier, means for regulating theoperational speed of said carrier-moving means, and automatic meansoperating in timed relation to the conveyor for controlling the supplyof'coating material to each atomizing device, said automatic means alsooperating to control said speed-regulating means to vary the speed ofthe carrier in predetermined manner as the carrier proceeds through itscycle of movement.

6. Electrostatic spray-coating apparatus, comprising a conveyor forconveying through a coating zone a succession of articles to be coated,a plurality of atomizing devices for spraying liquid coating material onto each article as it passes through the coating zone, means including ahigh-voltage source for creating an electrical charge differentialbetween the spray particles and an article in the coating zone, at leastone of said atomizing devices being mounted on a swivelled support andcomprising a rotating atomizing head from the periphery of whichatomization of the coating material takes place, said head beingmaintained at high voltage by connection to said high-voltage source,said swivelled support having rigid with it a sleeve the axis of whichis transverse to that of said head, means including a shaft extendingaxially within said sleeve for rotating said head, power operated meansfor rotating said sleeve about its axis, and automatic means operatingin timed relation with the conveyor for controlling said power-operatedmeans.

7. Electrostatic spray-coating apparatus, comprising a conveyor forconveying through a coating zone a suc cession of articles to be coated,a plurality of atomizing devices for spraying liquid coating material onto each article as it passes through the coating zone, means including ahigh-voltage source for creating an electrical charge diiferentialbetween the spray particles and an article in the coating zone, at leastone of said atomizing devices comprising a rotatable head from theperiphery of which atomization of the coating material takes place,

said head being maintained at high voltage by said highvoltage source, adriven shaft to which said head is fixed, a sleeve on which said shaftis rotatably mounted with its axis transverse to that of the sleeve, ahousing, a pair of spaced hollow brackets of insulating materialprojecting in generally parallel relation from said housing, bearingmeans at the outer ends of said brackets rotatably receiving the ends ofsaid sleeve, means including a first motor in said housing and a firstdrive shaft extending through one of said brackets for rotating saidsleeve about its axis, an intermediate shaft rotatably mounted withinand extending axially of said sleeve, gearing providing a drivingconnection from said intermediate shaft to said driven shaft, and meansincluding a second motor in said housing and a second drive shaftextending through the other of said brackets for driving saidintermediate shaft.

References Cited by the Examiner UNITED STATES PATENTS 2,729,189 1/1956Schweitzer et al. 118-323 X 2,736,671 2/1956 Ransburg et a1. 118631 X2,785,088 3/1957 Ransburg 11793.42 2,894,485 7/1959 Sedlacsik ll8323 X2,900,950 8/1959 Peeps 1182 2,955,568 10/1960 Blenman et a1 1182 X2,996,042 8/1961 Juvinall 11793.42 X 3,001,504 9/1961 Gengenbach et al.118-2 CHARLES A. WILLMUTH, Primary Examiner. PETER FELDMAN, AssistantExaminer.

5. ELECTROSTATIC SPRAY-COATING APPARATUS, COMPRISING A CONVEYOR FOR CONVEYING THROUGH A COATING ZONE A SUCCESSION OF ARTICLES TO BE COATED, A PLURALITY OF ATOMIZING DEVICES FOR SPRAYING LIQUID COATING MATERIAL ON TO EACH ARTICLE AS IT PASSES THROUGH THE COATING ZONE, MEANS INCLUDING A HIGH-VOLTAGE SOURCE FOR CREATING AN ELECTRICAL CHARGE DIFFERENTIAL BETWEEN THE SPRAY PARTICLES AND AN ARTICLE IN THE COATING ZONE, AT LEAST ONE OF SAID ATOMIZING DEVICES BEING MOUNTED ON A CARRIER ARRANGED FOR MOVEMENT TRANSVERSELY OF THE PATH OF ARTICLE MOVEMENT, POWEROPERATED MEANS FOR CYCLICALLY MOVING SAID CARRIER, MEANS FOR REGULATING THE OPERATIONAL SPEED OF SAID CARRIER-MOVING MEANS, AND AUTOMATIC MEANS OPERATING IN TIMED RELATION TO THE CONVEYOR FOR CONTROLLING THE SUPPLY OF COATING MATERIAL TO EACH ATOMIZING DEVICE, SAID AUTOMATIC MEANS ALSO OPERATING TO CONTROL SAID SPEED-REGULATING MEANS TO VARY THE SPEED OF THE CARRIER IN PREDETERMINED MANNR AS THE CARRIER PROCEEDS THROUGH ITS CYCLE OF MOVEMENT. 